Selecting a Rear Wheel Depth

FLO Product Support, FAQ, Cycling, Triathlon, Etc.

Selecting a Rear Wheel Depth

Postby chastaca » February 27th, 2017, 10:15 am

Hello all:

I have seen lots of discussion regarding front wheel selection, but I couldn't find many clear answers on this subject addressed in the forum. Feel free to redirect me if I missed this.

I recognize that front wheel depth selection is more important due to the potential impact of crosswinds on the moveable steering axis. I also have reviewed prior moderator responses that state in general, a rider should select the most aero front wheel that they can consistently control in all but the most extreme hill climb situations.

However, what about the rear wheel for road riding (i.e. excluding disc wheels used for triathlons or time trials)? I understand that most riders can easily control a 90 mm rear wheel due to weight distribution and the lack of a steering axis. If that is the case, why would one choose a 60 mm rear wheel over a 90 mm rear wheel? Are there issues with "too big" of a gap between a front wheel depth and a rear wheel depth (i.e. coupling a front 30 mm or 45 mm wheel with a 90 mm depth or disc rear wheel)? Are there true benefits to getting different sizes between the front and rear depths, or are there some benefits to equal distribution depths between the front and rear as well?

(For context, I am 6'00" and weigh about 160-165 lbs. I anticipate purchasing either a Flo 45 or Flo 60 as my front "do everything" wheel for both road and triathlon riding. I am trying to choose between a rear 60 mm or rear 90 mm, but can't see any particular logic in getting the 60 mm rear unless I am missing something).

Thank you for your thoughts and comments!

Cody
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Re: Selecting a Rear Wheel Depth

Postby Chris Thornham » February 28th, 2017, 7:55 am

chastaca wrote:Hello all:

I have seen lots of discussion regarding front wheel selection, but I couldn't find many clear answers on this subject addressed in the forum. Feel free to redirect me if I missed this.

I recognize that front wheel depth selection is more important due to the potential impact of crosswinds on the moveable steering axis. I also have reviewed prior moderator responses that state in general, a rider should select the most aero front wheel that they can consistently control in all but the most extreme hill climb situations.

However, what about the rear wheel for road riding (i.e. excluding disc wheels used for triathlons or time trials)? I understand that most riders can easily control a 90 mm rear wheel due to weight distribution and the lack of a steering axis. If that is the case, why would one choose a 60 mm rear wheel over a 90 mm rear wheel? Are there issues with "too big" of a gap between a front wheel depth and a rear wheel depth (i.e. coupling a front 30 mm or 45 mm wheel with a 90 mm depth or disc rear wheel)? Are there true benefits to getting different sizes between the front and rear depths, or are there some benefits to equal distribution depths between the front and rear as well?

(For context, I am 6'00" and weigh about 160-165 lbs. I anticipate purchasing either a Flo 45 or Flo 60 as my front "do everything" wheel for both road and triathlon riding. I am trying to choose between a rear 60 mm or rear 90 mm, but can't see any particular logic in getting the 60 mm rear unless I am missing something).

Thank you for your thoughts and comments!

Cody


Cody,

Thanks for writing, and great question. You've pretty much got the logic right. There really isn't a particular reason to not get the rear FLO 90 for your type of riding. There are a couple of reasons.

1. As you said without a steering axis, the rear wheel isn't hard to control in crosswinds. For this reason, you pick the fastest wheel, and in most cases for your type of riding, that is the rear FLO 90.

2. Your ratio of depth between the front wheel and the rear wheel matters. As the rear wheel gets bigger in relation to the front wheel you move your center of pressure towards the back end of the bike. This will help stabilize you in a cross wind. So this means a 45/90 will be more stable than a 60/90, which will be more stable than a 60/60.

I hope this helps. Please let me know if you have any additional questions.

Take care,
Chris Thornham
FLO Cycling: http://www.flocycling.com
FLO Blog: http://bit.ly/b3Zlpq | Twitter: http://bit.ly/bOQ08x | Facebook: http://bit.ly/d8KDhI
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Re: Selecting a Rear Wheel Depth

Postby PsychoMike » March 1st, 2017, 11:16 am

I'm going to potentially muddy the water a little here a bit more for you, Cody.

Flo has done some pretty impressive work and research on yaw angles and found that yaw angles are generally less than 10 degrees. The redesign of the 2016 wheel was based on the fact that 80% of the time, we're riding in less than 10 degrees of yaw and the Flo wind tunnel results show the 60 is a little better at lower yaw angles.

If you're more of a fast road rider, especially one who picks the day's riding route with the wind in mind or rides in a group a bit more often, then perhaps the 60 might be a hair bit faster. Hiding from winds in the group or being able to pick your route for head/tail winds pushes you more into the smaller yaw angles where the 60 performs a little better.

If you're doing a fair bit of tri work, I would agree that the 90's is probably the better choice. As Chris has said, the 90 is slightly quicker on the 40 km and IM events and provides a little bit more stability. Coupled with the greater ease of adding a disc cover to a 90 (less cover material to fight with) and a hair more weight (for a hair bit more "fly wheel" effect), it may be the "for sure" winner.

Regardless, it is a wonderful dilemma to be in :)
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Re: Selecting a Rear Wheel Depth

Postby chastaca » March 5th, 2017, 8:24 pm

Thanks both to Chris and to PsychoMike for your thoughtful answers and insight! That helps clarify things a lot. Looking forward to the next Order release!
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